1. Field of the Invention
This invention relates to protecting moisture-sensitive components from moisture. In particular, the invention is directed to a method for protecting integrated circuits from moisture accumulated during back-end testing.
2. Background
After the traditional bum-in testing of electronic components, various testing steps are performed under ambient conditions. The conventional sequence of steps used in the back-end processing of an integrated circuit is shown in FIG. 1. Throughout back-end testing, and especially during the intervals between each test, the integrated circuits are exposed to moisture. To provide customers with components having a maximum floor life, it is conventional to bake components prior to shipment. The baking step removes any moisture introduced during back-end testing, thereby producing dry components. It is important to remove all moisture lingering on plastic encapsulated IC packages, as otherwise excess moisture can induce package cracking upon mounting a package onto a board. The aforementioned baking step is typically performed at 125xc2x0 C. between 16 and 24 hours. To ensure that customers will be given adequate time (typically 168 hours) to use the ICs after removal from their container, a need exists for modifying the conventional back-end processing of moisture sensitive components.
The present invention provides a method to protect moisture-sensitive components from undesirably high moisture exposure during back-end testing after bum-in. Bum-in comprises elevating the ambient temperature surrounding a semiconductor package while an electrical load is applied to the die.
Moisture-sensitive components that may be protected in accordance with the present invention include plastic encapsulated integrated circuits, and other goods that are at risk of being damaged by undue exposure to moisture.
The method of the invention encompasses protecting a moisture sensitive component from exposure to moisture above a predetermined threshold level. A moisture sensitive component is placed into a container with desiccant and then sealed. Once, the moisture sensitive components are to be evaluated, the container is unsealed and the components removed from their container. After evaluation, the components are restored to the container, which is then resealed. The above steps are repeated until the components are placed into their container for either shipment, or transportation outside the local testing environment. The protective container is any type of enclosure that minimizes the exposure of moisture-sensitive components to the ambient environment. Due to the effectiveness in stemming moisture accumulation, a balding step is not necessary immediately prior to shipment.